1. Field of the Invention
The invention relates to a device for producing directional vibrations.
2. Description of the Related Art
Devices of this kind are known and are used to introduce directional vibrations into a structure. The structure can be a vibrating table for compacting concrete or an implement, e.g. a vibrating plate for soil compaction. In the case of vibrating tables, the directional vibrations are predominantly produced by vibrators positively synchronized by electrical/electronic or mechanical means or by pendulum vibrators.
The vibrators are two centrifugal weights which rotate in opposite directions and the mutually opposed centrifugal-force components of which cancel each other out, while the force component plane in the drawn perpendicularly to that through the axes of rotation of the centrifugal weights add up to give a resultant force and effect the vibration. The centrifugal weights are synchronized in a mechanical, electrical or electronic manner, in some cases with considerable complexity. To avoid the occurrence of damaging forces in a direction transverse to the actual direction of vibration, considerable precision of synchronization is required.
In the case of soil compaction equipment, especially vibrating plates, as in the case of vibrating tables, it is known that a purely directional vibration can be obtained by rotating two centrifugal weights with the same m x r (where m x r is the product of the mass of the unbalance weight and the radius of the center of gravity) in opposite directions at the same speed about mutually parallel axes. For this purpose, the unbalance weights in the known equipment, are mounted in a common housing and are coupled positively to one another for rotation and are both driven in opposite directions at the desired identical speed by a common drive.
Particularly when using vibrating tables, the known way of producing directional vibrations has proven problematic because of the high degree of design complexity associated with it and the costs this entails.
A device of this kind is known from GB-A-2 103 333. The device described has, inter alia, inflatable chambers, the variable stiffness of which determines the intensity of the vibration produced by centrifugal weights on a bracket.